What does the term "ground effect" refer to?

The term "ground effect" refers to a phenomenon that occurs when an aircraft is flying close to the ground, typically within one wingspan's distance. This proximity to the ground alters how lift and drag behave around the aircraft. Specifically, as the aircraft approaches the ground, the airflow beneath the wings is compressed, which enhances lift. At the same time, ground effect reduces the induced drag that an aircraft typically experiences at higher altitudes.

This effect is most pronounced during takeoff and landing phases, where a pilot may notice that the aircraft feels more buoyant and requires less power to maintain altitude than it would at a higher elevation. Understanding ground effect is critical for pilots, as it can influence their approach and landing techniques, especially in smaller aircraft where this effect is more prevalent.

Seeing that the other options describe unrelated phenomena, they do not reflect the specific aerodynamic principles associated with ground effect. For instance, turbulence at high altitudes doesn't relate to wing dynamics near the surface, visibility issues stem from atmospheric conditions rather than ground proximity, and exhaust fumes are not linked to the aerodynamic lift or drag changes that happen in ground effect.